Catalytic conversion



Patented Dec. 14-, 1943 2,337,015 CATALYTIC CONVERSION Chester C. Crawford, Bartlesville, Okla; and' William E, Ross, Berkeley, Calif., assignors to Shell Development Company, San Francisco, Calif., a, corporation of Delaware 1 No Drawing. Original application eptember 22,- 1942, Serial No.- 459,326. Divided and this application May 5, 1943, Serial No. 485,947

12 Claims. (Cl. 260-6835) This invention relates to improved catalytic conversions executed withthe aid of aluminum halide-containing catalysts.

The aluminum halides are known to possess the ability to catalyze a great number of chemical reactions. Because of its availability and relatively low cost, the use of the chloride is generally preferred. Many of the aluminum ch ride catalysts utilized heretofore, however, possess distinct disadvantages which often render their use on a practical scale difiicult, if not im possible. Aluminum chloride either per se or supported upon a support material generally does not permit the attainment of the degree of contact between catalyst and material being treated required to obtain the most efiicient results. This is particularly so when operating in the liquid phase; and many processes, such as, for example, the treatment or conversion of hydrocarbons, are often eliected more advantageously in the liquid phase; A- further disadvantage often in- -herent in the use of solid aluminum chloride catalysts resides in the difliculty with which a desired catalyst bed temperature can be effectively maintained, due to the poor heat conductivity of most of these catalysts. Since a considerable portion of these solid catalysts often consists of the inert support material, a relatively large reaction zone is generally needed for relatively small amounts of the active catalyst constituent.

The use of aluminum chloride in the molten state is entirely unsatisfactory because of its high melting point and relatively high volatility. Modified forms of aluminum chloride catalysts comprising, for example, aluminum chloride in admixture with other halide salts which have been proposed. Certain 'of these mixtures possess melting points which are appreciably lower than that of aluminum chloride. However, such mixed catalysts, when used in the compositions at which they. possess desirable catalytic activity general- .ly still possess melting points which are sumciently high not only to prevent their eificient use in reactions which must be conducted at relatively low temperatures, but to entail serious difiiculties in moving the catalysts in their molten form through the system. To avoid the latter difiiculty means must be resorted to, such as, for example, the heating or elaborate la ging of pipes to prevent the freezing of any part of the catalyst therein. Sludge-type catalysts, such as organic aluminum chloride complexes, have a relatively limited field of application and these also present serious diificulties not only in the handling of these materials within the system, but in their separation from the product. The complex catalysts generally become quite viscous at low temperatures, often approaching the consistency of a paste at temperatures of, for example, about 20 0., thereby rendering extremely difficult the movement of the catalysts within the system and also making difficult, if not impossible, the obtaining of a proper degree of contact between the catalyst and the material being treated. Slight amounts of impurities in the charge, furthermore, aid in quickly increasing the viscosity of such sludge-type catalysts at the lower temperatures to a point where the duration of theoperation is far below that permissible in a practical operation. It is, therefore, readily apparent that aluminum halide-containing catalysts of high activity which are able to maintain their fluidity and activity at relatively low temperatures in the absence of the above-described execution of eatalytidreactions in the liquid phase in the presence of fluid catalysts comprising an aluminum halide.

Another object of the invention is the provision of an improved process for the more efficient treatment of hydrocarbons in the liquid phase with the aid of fluid aluminum chloridecontaining catalysts. Other objects and advantages of the invention will become apparent from the following detailed description thereof.

The improved catalysts of the invention are obtained by combining an aluminum halide, such as, for example, aluminum chloride with ahalide salt of a cyclic nitrogen base containing the nitrogen atom within the ring, such as, for example, a halide salt of pyridine, pyrollidine,

quinoline, alkyl derivatives thereof, etc. Of the halide salts of the cyclic nitrogen bases the chlorides are generally preferred. The catalysts of the invention are not necessarily'limited, however, to those containing only chloride salts, and

components in the catalysts may vary within the scope of the invention in accordance with the particular characteristics of the catalyst desired,

operating conditions at which they are to be employed, the nature of the material to be treated, and the like. The degree of catalytic activity, as well as other properties of the catalysts affecting their efficient use under particular operating conditions, are, however, dependent upon their composition. Since thealuminum halides react tion of aluminum chloride to the mixture above the equimolecular amount results in catalysts particularly suitable for catalyzing hydrocarbon reactions. When utilizing the catalysts in the liquid state the temperature of a particular operation will govern the content of A1013 in the catalyst. Mixtures of aluminum chloride and pyridine hydrochloride containing from 50 to 83 percent by weight of AlCla have a maximum melting point of about 150 0., whereas those having an aluminum chloride content of from about 63 v to '77 percent by weight have a maximum melting point of only about 80 C. Catalyst mixtures consisting of or approaching the eutectic composition are particularly preferred. The eutectic composition consisting of 66 percent by weight of aluminum chloride and 34 percent by weight of Pyridine hydrochloride pyridine hydrochloride melts below approximately C. The solutions of aluminum chloride in pyridine hydrochloride, however, possess the very attractive feature of being able to undergo supercooling to an unusual degree, and their melting points are therefore not indicative of the minimum temperature at which they can be used efiiciently in the liquid state. Thus, the aluminum chloride-pyridine hydrochloride cat alyst containing about 66 percent by weight of AlCls, though possessing a melting point of approximately 40 0., can be used efliciently in the liquid state not only at room temperature (20 C.) but at temperature as low as 0 C.

It is apparent from the foregoing that the invention provides aluminum halide catalysts which can be used in the liquid state at lower temperatures than has been possible with the aluminum halide-containing catalysts available heretofore; The catalysts of the invention are particularly suited for use in the execution of catalytic proc-'- esses which must be effected, either preferably or of necessity, in the liquid phase at relatively low temperatures. The catalysts are particularly applicable to the execution of many hydrocarbon reactions such as alkylation, or the isomerization of the more readily degraded par-aflinic hydrocarbons. It is well known that paraflinic hydrocarbons having more than four carbon atoms to the molecule, particularly pentane, undergo substantial decomposition in the presence of active aluminum halide catalysts at temperatures as low as C. -Such decomposition not only results in considerable loss of the material treated but results in the rapid degradation of the catalyst activity due to the presence of by-products formed. Since a great many of the aluminum halide catalysts available heretofore melt at temperatures substantially in excess of even C., it is apparent that such catalysts are not suitable for the-isomerization of pentane in the liquid phase. Though certain mixtures of molten salts fcomprising aluminum chloride have melting points below 100 C., the relatively narrow temperature range between the minimum temperature at which these mixtures can be maintained in the liquid phase and the maximum temperature at which they can be used for the isomerization of saturated hydrocarbons having at least five carbon atoms to the molecule, is generally. toosmall to assure complete freedom from the danger of freezing at least a part of the catalyst within the system, or to enable any substantial variation in catalyst composition. The greater fluidity of the catalysts of the invention at the lower temperatures on the other hand presents a distinct advantage over catalyst mixtures possessing higher viscosities at the temperature or operation since the'conversion obtained depends greatly on'the contact efilciency which in turn is a direct function of the viscosity of the liquid catalysts. The catalysts of the invention are also free of the salt components more readily soluble in hydrocarbons, so often present in mixed salt catalysts used heretofore, and there fore eliminate the need for a subsequent operation to remove dissolved catalyst from the prod- 110135. I

Illustrative of the type of catalytic reaction to Which the catalysts of the invention can be applied with particular advantage in the liquid state is the isomerization in the liquidphase, at relatively low temperature conditions, of the more readily degraded hydrocarbons, such as, for example, the conversion of normal or branched chain saturated hydrocarbons having at least five carbon atoms to' the molecule to branched or more highly branched chain saturated hydrocarbons having the same number of atoms to the molecule. This is illustrated by the following example Example amount of 4 percent by weight of the pentane treated was introduced into the reactor. Temperature of operation, time of contact and amount of isopentane' obtained in percent by weight of the total hydrocarbons removed from the reactor are indicated in the following table:

Temperature Time of contact Isopentane "0. Percent 40 30 min 22. 3 40 2 hrs 34. 3 60 15 min 57. 2

The invention thus enables the isomerization of hydrocarbons with the aid of a liquid aluminum halide-containing catalyst at temperatures considerably lower than possible heretofore. The possibility of attaining equilibrium mixtures containing higher proportionsof isoparafiins to normal parafiins at the lower temperatures, taken together with the ease with which the process can be executed at these lower temperatures be isomerized in the liquid phase.

employed, contribute considerably to ofiset the apparent advantages of more rapid isomerization rates at higher temperatures.

The isomerization of isomerizable hydrocarbons in the liquid phase in the presence of the catalysts of the invention utilized in the liquid state is preferably executed at a temperature not substan tially in excess of about 70 C., and the more readily degraded hydrocarbons, such as, for example, pentane, are preferably isomerized at a temperature not substantially in excess of about 65 C. A sufiiciently high pressure is maintained to keep the reactants in the liquid phase.

Though pentane has been chosen as the isomerizable saturated hydrocarbon in the above example, it is to be pointed out that-the invention is not limited to the isomerization in the liquid phase of a specific hydrocarbon, and that other isomerizable hydrocarbons having more than five carbon atoms to the molecule, such as the saturated hydrocarbons having from live to ten carbon atoms to the molecule, may advantageously The charge need, furthermore, not necessarily comprise but a single hydrocarbon and may contain other hyisomerization under the. conditions of execution of the process. Thus, when treating a mixture of hydrocarbons comprising butane and pentane under the above specified conditions, pentane is found to be "selectively isomerized. The liquid phase isomerization process is also applicable to the isomerization of other than open chain paraffin hydrocarbons. It may be applied, for example, to the isomerization of naphthenic hydrocarbons, such as methyl cyclopentane, dimethyl cyclopentane, methyl cyclohexane, dimethyl cyclohexane, etc. Hydrocarbon fractions comprising substantial amounts of isomerizable saturated hydrocarbons, such as, for example, fractions of straight run gasoline, casingheadgasoline, etc., may be treated under the liquid phase isomerizing conditions to produce products suitable for' alkylation with olefins and which have improved ignition characteristics.

-Illustrative of other processes to which the catalysts of the invention may be applied with advantage in the liquid state at relatively low temperatures are the treating or refining operations wherein hydrocarbons or hydrocarbon mixtures are subjected to contact with a liquid-treating agent. A particular application is their use in the treatment of lubricating oils or lubricating oil-containing fractions to efiect the removal of impurities therefrom. The lubricating oils or lubricating oil fractions and the catalysts in the liquid state may be contacted in concurrent or countercurrent flow for a time sufiiciently long .to effect the desired purification and improvement of the lubricating oil, whereupon the catalyst and hydrocarbons are separated and the catalyst optionally recycled to the treating zone.

It is to be understood that the above examples are but a few of the many reactions conducted at relatively low temperatures in which the catalysts of the invention can be applied with advantage in the, liquid state, and that the application of the novel catalysts is not limited thereto.

Though the catalysts of the invention can be applied with particular advantage to processes in catalytic processes involvin the execution of reactions at higher temperatures and wherein the reactants may optionally be in the vapor phase. Thus,-.the fluid catalysts of the invention may be applied to such processes conducted at higher temperatures as those comprising, for example, the degradation of hydrocarbons; conversion of higher boiling hydrocarbons into lower boiling hydrocarbons; polymerization of normally gaseous olefinic hydrocarbons; isomerization of the less readily degraded hydrocarbons, such as, for example, butane; hydrocarbon reversion operations wherein normally liquid hydrocarbons are contacted with the catalyst in the presence of lower boiling, preferably gaseous hydrocarbons, whereby interaction of the lower boiling and higher boiling hydrocarbons is brought about simultaneously with conversion reactions the specific nature of which reactions are dependent drocarbons which may or may not be capable of manner.

executed in the liquid phase at relatively low tem- V peratures, their application is not necessarily limited thereto. The catalysts of the invention may also be utilized in the fluid state as catalysts upon the operating conditions used; chlorination of hydrocarbons, etc.

The catalysts of the invention may be utilized in the presence of suitable promoting agents which may vary in nature and in amounts used in accordance with particular operating conditions and the nature of the reaction. Thus, the ability of the catalysts to catalyze hydrocarbon reactions, such as, for example, isomerization and alkylation, is generally enhanced by the presence of a hydrogen halide, such as, for example, hydrogen chloride, or compounds capable .of liberating a hydrogen halide under the reaction conditions. In the execution of hydrocarbon reactions wherein hydrocarbon decomposition is undesired, materials capable of suppressing such side reactions as, for example, hydrogen, may be introduced into the reaction zone.

The catalysts of the invention lend themselves to efiicient application in processes conducted batchwise, intermittently, or in a continuous It is to be pointed out, however, that the nature of the catalysts renders them particularly advantageous to utilization in continuous processes, comprising, for example, the utilization of externally heated, elongated reaction zones of restricted cross-sectional areas through which the catalyst and reactants are passed in concurrent flow. Efliuence from such reaction zones may be passed to a separating zone, wherein, the catalyst may be separated readily from the reactants and optionally recycled to the reaction zone.

The marked advantages of the catalysts of the invention in the liquid state over aluminum halide-containing catalysts available heretofore has been stressed. It is to be pointed out, however, that the novel catalysts in the solid state, as

well as their use in catalytic process, are not to be considered beyond the scope of the present invention. The catalysts in the solid state may be deposited upon any suitable support material comprising, for example, aluminum oxide, magnesiur'n oxide, bauxite, kieselguhr, silica, silica gel, pumice, majolica chips, carbon, adsorbent clays, or support materials. The support materials may be subjected to the activating treatments well known in the art prior to being impregnated with the aluminum halide catalysts. The solid catalysts may, furthermore, be modified by the presence of other salts comprising, for example, the halides of the alkali or alkaline earth metals.

This application is a division of co-pending 7 application Serial No. 459,326 filed September.

We claim as our invention:

1. An isomerization process which comprises contacting hydrocarbons comprising an isomerizable hydrocarbon having at least 5 carbon atoms to the molecule'at a temperature not substantially in excess of about 65 C. with a molten catalyst comprising aluminum chloride and pyri-' dine hydrochloride, said catalyst containing about 66% by weight of aluminum chloride.

2. Process for the conversion of normal pentane to isopentane' which comprises contacting hydrocarbons comprising normal pentane at a temperature not substantially in excess of about 65 C. with a catalyst consisting of a molten mixture of aluminum chloride and pyridine hydrochloride, said mixture containing from about 63% to about 72% by weight of aluminum chloride.

3. A process for the conversion of normal paraffin to branched chain parafiins which comprises contacting hydrocarbons comprising a normal paraffin at a temperature not substantially in excess of about 65 C. with a catalyst consisting of a molten mixture of aluminum chloride and pyridine hydrochloride, said mixture containing from about 63% to about 72% by weight of aluminum chloride.

4. A process for the conversion of normal and branched chain isomerizable saturated hydrocarbons to branched and more highly branched chain saturated hydrocarbons which comprises contacting hydrocarbons comprising normal and branched chain isomerizable saturated hydrocarbons at isomerizing conditions with a molten mixture comprising an aluminum halide and pyridine hydrochloride, said mixture containing the aluminum halide in molecular excess.

' 5. Anisomerization process which comprises contacting hydrocarbons comprising an isomeriza catalyst comprising aluminum chloride in admixture with pyridine hydrochloride, said cata-- 6. An isomerization process which comprises 45 able hydrocarbon at isomerizing conditions with contacting hydrocarbons comprising an isomerizable hydrocarbon at isomerizing condition with a catalyst comprising an aluminum halide in admixture with pyridine hydrochloride, said catalyst containin the aluminum halide in molecular excess. p

'7. An isomerization process which comprises contacting hydrocarbons comprising an isomerizable hydrocarbon at isomerizing conditions with a molten mixture of an aluminum halide and the salt of pyridine and a hydrogen halide, said mixture containing the aluminum halide in molecular excess.

8. An isomerization process which comprises contacting hydrocarbons comprising an isomerizable hydrocarbon at isomerizing conditions with a catalyst comprising an aluminum halide in admixture with pyridine hydrochloride, said catalyst containing a molecular excess of aluminum chloride.

9. An isomerization process which comprises contacting hydrocarbons comprising an isomerizable hydrocarbon at isomerizing conditions with a catalyst comprising an aluminum halide in admixture with a halide salt of a cyclic nitrogen base, said catalystcontaining the aluminum halide in molecular excess.

10. An isomerization process which comprises contacting hydrocarbons comprising an isomerizable hydrocarbon at isomerizing conditions with a catalyst comprising aluminum chloride in admixture with pyridine hydrochloride.

11. An isomerization process which comprises contacting hydrocarbons comprising an isomerizable hydrocarbon at isomerizing conditions with a catalystcomprising a halide salt of aluminum in admixture with pyridine hydrochloride.

12. An isomerization process which comprises contacting hydrocarbons comprising an isomerizable hydrocarbon at isomerizing conditions with a. catalyst'comprising a halide salt of aluminum in admixture with a halide salt of a cyclic nitrogen base.

-' CHESTER C. CRAWFORD.

' WILLIAM E. ROSS. 

